[arrays] Cloning an array in Javascript/Typescript

Cloning Arrays and Objects in javascript have a different syntax. Sooner or later everyone learns the difference the hard way and end up here.

In Typescript and ES6 you can use the spread operator for array and object:

const myClonedArray  = [...myArray];  // This is ok for [1,2,'test','bla']
                                      // But wont work for [{a:1}, {b:2}]. 
                                      // A bug will occur when you 
                                      // modify the clone and you expect the 
                                      // original not to be modified.
                                      // The solution is to do a deep copy
                                      // when you are cloning an array of objects.

To do a deep copy of an object you need an external library:

import {cloneDeep} from 'lodash';
const myClonedArray = cloneDeep(myArray);     // This works for [{a:1}, {b:2}]

The spread operator works on object as well but it will only do a shallow copy (first layer of children)

const myShallowClonedObject = {...myObject};   // Will do a shallow copy
                                               // and cause you an un expected bug.

To do a deep copy of an object you need an external library:

 import {cloneDeep} from 'lodash';
 const deeplyClonedObject = cloneDeep(myObject);   // This works for [{a:{b:2}}]

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Examples related to angular

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Examples related to typescript

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